1. Field of the Invention
The present invention relates to a non-contact type data reception and transmission body as an information recording media for RFID (Radio Frequency IDentification) use which can receive information from outside and transmit the information outside using electromagnetic waves as a medium.
This application claims priority of Japanese Patent Application No. 2004-368091, filed Dec. 20, 2004, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In recent years, a non-contact type data reception and transmission body as an information recording media for RFID (Radio Frequency IDentification) use such as a non-contact IC (integrated circuit) tag, and the like has been proposed in which information can be received from the outside and can be transmitted to the outside using electromagnetic waves as a medium.
In an IC label, which is an example of the non-contact type data reception and transmission body, when the electromagnetic waves from a reader/writer are received, an electromotive force is generated at an antenna by resonance action, an IC chip within the IC label is booted by the electromotive force, information within the IC chip is converted to signals, and the signals are transmitted from the antenna of the IC label.
The signals transmitted from the IC label are received by the antenna of the reader/writer, and are transmitted to a data processing apparatus via a controller, and data processings such as identification, and the like are performed.
In order for the IC label to be operated, although the electromagnetic waves transmitted from the reader/writer are fully received by the antenna of the IC label, an electromotive force greater than the operation electromotive force of the IC chip must be induced, and when the IC label is attached on the surface of a metallic article, magnetic flux becomes parallel with respect to the metallic article at the surface of the metallic article. Therefore, a problem occurs in which, because the magnetic flux across the antenna of the IC label decreases, and the induced electromotive force decreases, the induced electromotive force is less than the operation electromotive force of the IC chip, and the IC chip does not operate (see for example, Non Patent Document 1: Supervision by Nobuyuki Teraura, “Development and Application of RF tag—Future of Wireless IC chip—”, First edition, CMC Publishing Co., Ltd., Feb. 28, 2003, Page 121, FIG. 2)
FIG. 3 is a schematic view showing a flow of magnetic flux in the case in which an IC label is disposed on a surface of a metallic article. Because a magnetic flux 102 generated from a reader/writer 101 becomes parallel at the surface of a metallic article 103, the magnetic flux that passes through an antenna 105 of an IC label 104 disposed on the surface of the metallic article 103 decreases, and an electromotive force induced at the antenna 105 decreases, and thereby an IC chip 106 does not operate.
Then, in order for the IC chip to operate on the metallic article, a method is proposed in which the antenna is wound around a ferrite core, the ferrite core is disposed so that an axial center of the antenna becomes parallel with respect to a direction of the magnetic flux at the surface of the metallic article, the magnetic flux that passes through the surface of the antenna is increased, and thereby the induced electromotive force is increased (see for example, Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2003-317052).
FIG. 4 is a perspective view of an IC tag according to an embodiment of Patent Document 1, and in FIG. 4, an antenna 111 is wound around the circumference of a square-shaped ferrite core 115, and on a part where the antenna 111 is not wound, an IC chip 112, condenser 113, and the like are mounted on the ferrite core 115 via a base substrate 114.
When a plane surface part (undersurface in FIG. 4) of the square-shaped ferrite core 115 of the IC tag is attached to the surface of a metallic article, because the magnetic flux parallel to the surface of the metallic article passes through the ferrite core 115, since the magnetic flux passes perpendicularly through the inside of the antenna 111, a desired inductive voltage occurs, and the IC chip 112 operates.
On the other hand, there is a proposal in which the antenna is formed in a plane shape, the magnetic flux passes through a magnetic core member provided on the undersurface of the antenna, and thereby the magnetic flux passes through the inside of the antenna formed in the plane shape, an induced electromotive force is generated in the antenna, while a conductive member is provided on the undersurface of the magnetic core member, and thereby a deleterious influence on the IC label from the article on which the IC label is disposed is prevented (for example, Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2003-108966).
FIG. 5 is a cross-sectional view showing an embodiment of Patent Document 2. An antenna 121 for the IC label is made of a conductor 121a circinately wound within the plane surface, and is provided with a plate-shaped or sheet-shaped magnetic core member 123 adhered to a side surface of the antenna 121 for the IC label, and a conductive material portion 124 on the undersurface of the magnetic core member 123.
The magnetic core member 123 is laminated on another surface of the base substrate to which the antenna 121 for the IC label is provided so that, crossing a part of the antenna 121 for the IC label, one end portion of the magnetic core member 123 is positioned at the outside of the antenna 121 for the IC label, and another end portion of the magnetic core member 123 is positioned at the central portion (inside) of the antenna 121 for the IC label.
When the magnetic core member 123 is laminated as such, because the magnetic flux enters from one end portion of the magnetic core member 123, and leaves from another end portion, the magnetic flux that has left another end portion passes through the inside of the antenna 121 for the IC label, and thereby an electromotive force is induced in the antenna 121 for the IC label made of the conductor 121a. Therefore, even if the IC label is attached to the surface of an article 125, and the direction of the magnetic flux on the circumference of the IC label becomes parallel with respect to the surface of the antenna 121 for the IC label, the magnetic flux passes through the inside of the antenna 121 for the IC label. Therefore, because a voltage which is sufficient for operating the IC chip is induced, the IC chip reliably operates.
Furthermore, in the present embodiment, because the conductive member 124 is laminated and attached to another surface of the base substrate to which the antenna 121 for IC label is provided so that the magnetic core member 123 is covered, the conductive member 124 shuts off the passing of the radiowave for the article. Therefore, the antenna 121 for IC label is hardly affected by the article 125 regardless of whether the article 125 is a metal or not, and even if the surface of the article 125 is made of a metal, loss due to an eddy current generating on the metal surface, or the like does not occur, and the IC label reliably operates in the case in which the IC label is attached to the metallic article 125.
However, in Patent Document 1, a problem occurs in which, in order to increase the induced electromotive force, when a diameter of the antenna 111 is increased so that the magnetic flux passing through the antenna 111 is increased, the thickness of the IC label is increased.
On the other hand, in Patent Document 2, a problem occurs in which, because the magnetic core member and the conductive member are provided on one surface of the base substrate, the thickness of the IC label is increased.